A simple, rapid surface microspreading technique applied to mammalian spermatocytes and oocytes yields nuclei containing selectively stained synaptonemal complex (SC) complements for electron microscopy. Quantitative analysis shows the method to be suitable for SC karyotyping and for demonstrating synaptic behavior of autosomes and sex chromosomes. Predicated on evidence that lateral elements of the SC (axes) are paradigms of the chromosomes, a study of mouse chromosome rearrangements is projected, aimed at 1) assessing the microspreading method as a cytogenetic tool, 2) providing cytogenetic information about the rearrangements not accessible with existing methods, and 3) investigating the biological correlates of the rearrangements, such as their behavior in meiotic synapsis and crossing over, and their genetic and developmental consequences. Using translocation, duplication, inversion and deletion heterozygotes, quantitative analyses of SC's will be correlated with available cytogenetic data to test their accuracy and sensitivity, and to begin constructing SC genetic maps. Homologous synapsis at zygotene and "synaptic adjustment" leading to non-homologous SC formation in the rearrangements will be investigated to establish a) rules governing synapsis, and b) timing of crossing over with respect to events in meiosis.